Control system for electric motors.



RJLDEARBORN.

CONTROL SYSTEM FOR ELECTRIC MOTORS.

APPLlCATION FILED JULY 11. 19x2.

1 175,346. Patented Mar. 14, 1916.

FIELD A/P/VIATUFE- g LOWER- WITNESSES: XQEEENTOR I Y 7 BY w/ UNITEDsnares arlour OFFICE.

RICHARD J. DEARBORN", OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TOWES'IlING- HOUSE ELECTRIC AND MANUFACTURING COMPANY, A. GORPORATlION OFPEN N SZL- VANIA,

CONTROL SYSTEM. FOR ELECTRIC MOTORS.

Specification of Letters Patent.

Patented Mar. 14, 1916.

Application filed July 17, 1912. Serial No. 710,098.

To all whom it may concern:

. Be it known that I, RIC-HARD J. DEARBORN, a citizen of the UnitedStates, and a resident of Wilkinsburg, in the county of Allegheny andState of Pennsylvania", have invented a new and useful Improvement inControl Systems for Electric Motors, of which the following is aspecification.

My invention relates to controllers for 10 electric motors and it hasspecial reference to such controllers as are adapted to govern themotors of cranes or hoists.

One of the objects of my invention is to provide a controller of theclass above indicated that shall be relatively simple in arrangement andembody the armature and field magnet windings of a series motor and therelease of a mechanical brake permanently connected together.

Another object of my invention is to provide a controller which shallestablish, with a relatively few number ofmoving contacts, suchadditional circuit connections between the above specifiedinterconnected parts, as not only to enable the motor to either hoist orlower its load or to act as a generator to retard the load, but also toenable the mechanical brake to beapplied without interrupting theregenerative brak- 3 ing circuit of the motor.

In the accompanying drawings, Figures 1, 2, 3 and 4 are simple diagramsillustrating the different-circuit arrangements etfected by thecontroller of my invention, and Fig. 5 is a diagrammatic view of acomplete system of electric motor control embodying'my invention. Figs.6, 7, 8 and 9 are diagrams corresponding to Figs. 1, 2, 3 and 45 of amodified arrangement which is 40 also arranged in accordance with myinvention. v

Referring to Figs. 1 to 5, inclusive, electric current is supplied fromany suitable source, through circuit conductors l. and 2 and acontroller 3 to an electric motor 41-, having a series field magnetwinding 5 and an armature 6. The motor, when deenergized, is quicklybrought to rest it is in motion, or held stationary it it 1551b rest, bya mechanical brake 7 which is released by coil 8 when the motor is inoperation, as hereinafter pointed out.

The controller 3 is adapted to occupy an intermediate or? position 0, aplurality of hoisting positions a, h, c, d, c, f and g and a pluralityof lowering positions is,

x, g and z. Resistor sections 9, 10 and 11 are associated with thecontroller 3,. while the motor 4 and the brake 7 are intended to bemounted on the trolley or relatively movable member of a crane in orderto operate the hoisting drums. Since the operators cab is usuallymounted on the body of the crane, all connections between the controller3and the resistor sections 9,10 and 11,011 the one hand, and themotoriand the brake'i', on the other hand, must be established throughconductors which are stretched longitudinally of the crane body andsliding or rolling contacts which engage the stretched condoctors andare mounted on thetrolley of the crane.

One of the advantages of my controller arises from the fact that acomparatively few number of conductors and sliding con- 7 tact membersis required, while the operation or the'system allows the crane to behandled in a particularly advantageous manner.

The operation and circuit connections for 89 the system are as follows:Assuming that the controller 3 is moved to occupy the position a, acircuit is established from the line conductor 1, through a conductor12, a contact finger 13, a. contact member 14, a finger 15, the resistorsection-9, a conductor'iG, the field coil 5, the armature 6, the brakecoil 8, a conductor 17, the resistor section. 10,

a finger 18, a contact'member 19, a finger 20 and a conductor 21 to theopposite line conductor 2. Circuit connections are thus established asindicated in Fig. 1..- As the controller successively occupies thepositions 1), a, (21, e, f and g, the resistor sect ns 9 and 10 are bothgradually short circu so until the motor is connected directly acrossthe circuit in series relation with the brake coil. I

When energy is first supplied to the and to the coil of the brake, thebrak leased and the motor is so operated hoist the load. It will beobserved motor operates as aserie's motor for b. If it is now assumedthat it is desired to the load, the controller is first moved throughthe off position into the lowering position is. In this position,circuit connections are established as follows: from the line conductor1, through the conductor 12, the finger 13, a pair of contact members issupplied to the armature,

a bridging contact member 25, a contactmember 26, a finger 27, theresistor section 11, a conductor 28, the armature 6, a con.-

ductor 29, a finger. 30, a pair of contact members 31 and 32-, thefinger 20' and the conductor 21 to the opposite line conductor 2.Another circuit connection is also established, in this position, fromthe conductor 12, through the finger 13, the contact members 22, thefinger 15, the entire resistor sectinn 9, the conductor 16 and the fieldmagnet windingto the conductor 29, from which point, circuit iscompleted as before. Still another circuit is completed from theconductor 28, through the brake coil 8, the conductor 17, the resisbrsection (a portion of which is first short circuited by the engagementof a contact finger 33 with a contact member 34), the finger 18, thecontact members 32, the finger and the conductor-21, as before. Thecircuit connections for this position are clearly shown in Fig.2 of thedrawings.

The resistor 10 is so designed as to permit sufiicient energy totraverse the brake coil 8, to hold the brake in its released position, aportion of the resistor being short circuited as the controller is firstmoved into vthis position, in order to temporarily allow a relativelylarge current to traverse the brake coil and release the brake.

It will be observed that the armature and field magn 'sa windings areconnected in multiple circuit relation, with the armature currentreversed, for lowering the load, and that the current traverses thefield magnet winding 1n the same direction as in the hoisting positionsof the controller. The motor accordingly operates as a shunt motor todrive the load downward. In the position is, however, a relatively smallcurrent while the field magnet is strongly energized and, consequently,the motor tends to operate at a very "ductor 16 and the slow speed.Accordingly, if the load on the hoist is light and it is desired tolower the hoist rapidly, the controller maybe adjusted to occupy thesuccessive positions at, y and z, in which the short circuited portionof the resistor section 9 is gradually inserted into the field branch ofthe motor. By this means, the motor field is weakened, its speed isincreased, and a larger proportion of the current is supplied to themotor armature.

When the controller occupies its offf position, a local dynamic brakingcircuit is established from one terminal of the armature 6 through theconductor 28, a contact finger 33, a contact member 34, the contactmember 26, the conductor 25, the contact member-24, a contact finger 35,the confield magnet winding 5 t0 the opposite terminal of the armature.

' braking circuit which The circuit connections are clearly illustratedin Fig. 4. It is, therefore, that, not only in the releasing coil 8ofthe brake deenergized and the mechanical brake set, but also alow-resistance local dynamic braking circuit 's established whichassists the mechanical brake in immediately bring mg the motor to rest.

I In the first lowering position It, the portion ofthe resistor sectioncluded in the field branch of the motor circuit is short circuited, andthe energy supplied to'the' motor tends to drive the load downward at avery slow speed, as above indicated. Cons-quently, if the load on thehoist is sufiiciently heavy, it will drive the motor ata higher speedand cause it to deliver energy to the local dynamic braking circuit,which is then established, as shown in Fig. 2.' I

The arrangement of parts is such that the current delivered to the localcircuit from the motor armature traverses the field winding in the samedirection as the energy which is supplied from the line when the load islight and, consequently, there. is no danger of the field failing tobuild up. In fact, the direction of currentin the field is the samewhether the motor is operating to hoist or to lower the load or whetherthe motor is operating as a generator and is being driven by the load.

My invention has the advantage of permitting the setting of themechanical brake by interrupting the circuit of the brake releasing coilwithout opening the dynamic exists in all of the lowering positions andin the off position of the controller. This is obviously impossiblewith-systems of the same general character, heretofore proposed, inwhich the brake-releasing coil is included directly in the dynamicbraking circuit in the lowering positions and is excluded-by eithertemporarily breaking the dynamic braking cir cuit as the controller ismoved into the off position or by relying solely upon themechanicalbrake.

Referring to Figs. correspond to Figs. 1, 2, 3and 4:, the arrangementhere shown is similar to that already described, with the exception thatthe positions of the armature and field windings are exchanger. Y

The operation of the system is substantially the same as before but thecurrent in the field magnet winding is reversed in changing fromhoisting to lowering, although there is no change in the direction ofcurrent in the field winding when the controller occupies its loweringpositions and the motor changes to a generator and is driven above itsnormal speed by the load. I claim as my invention: 1. A hoist or cranecontrol system'comevident 6, 7, 8 and '9, which means for establishing'c1rcu1t for lowering that 1s independent of the brake-releasing coil.

. relationfor hoisting,

prising an electric motor having an armature and a series field magnetwinding, a brake-releasing coil included in series with the motorarmature and the field magnet winding for hoisting, and a controller forconnecting the motor armature, the field magnet winding and thebrake-releasing coil in parallel circuits for lowering, whereby adynamic braking circuit is established which is independent of saidreleasing coil. 2. A hoist or crane control system comprising anelectric motor having an arma-' tureand a field magnet winding, amechanical brake having a releasing coil, and controlling means forconnecting the armature, the field mz'ignet winding and thebrake-releasing coil in parallel circuits'for lowering.

3. A hoist or crane control system comprising an electric motor havingan armature and a field'magnet winding, a mechanical,v brake having areleasing coilnormally connected in series with the motor, and a dynamicbraking 4. In a hoist or crane control system, the combination with anelectric motor having an armature and a field magnet winding, and amechanical brake having a releasing coil, said armature, field magnetwinding and releasing coil being connected in series relation forhoisting, of a controller for reversing the motor and establishing adynamic braking circuit for lowering that is independent of saidreleasing coil.

5. In a hoist or crane control system, the combination with an electricmotor having an armature and a field magnet windin and a mechanicalbrake having a releasing coil, said armature, field magnet winding andreleasing coil being connected in series of a controller for connectingthe armature and field magnet windis established for lowering ing andthe brake-releasing coil in parallel paths, whereby a dynamic brakingcircuit that is independent of the releasing coil.

6. In a hoist or crane control system, the combination withan electricmotor having an armature and a field magnet winding, and a mechanicalbrake having a releasing coil normally in series with said motor, of aresistor normally in series with the releasing coil, a controller forreversing said motor, and means comprising said controller fortemporarily shunting a portion of said resistor when said motor isreversed for lowering. I

7 In a hoist or crane control system, the.

"combination with an electric motor having connected in series with.field winding, I

a coil, means for connecting said field W1I1Cl-- the motor andestablishing a dynamic braking circuit and for temporarily increasingthe current traversing said releasing coil when said motor is reversedfor lowering.

S. A hoist or crane control system comprising an electric motor havingan armature and a field magnet winding, a mechanical brake having areleasing coil normally the motor, and dynamic braking is independent ofcoil and is maintained the said coil is intermeans for establishing acircuit for lowering that the brake-releasing while the circuit ofrupted.

9. A hoist or crane control system comprising an electric motor havingan armature and a field magnet winding, a mechanical brake having areleasing coil, said armature and field magnet windings and releasingcoil; being connected in series relation for hoisting, and a controllerfor reversing the motor and establishing a dynamic braking circuit forlowering that is independent of the brake-releasing coil and Y ismaintained while the circuit of the said coil is interrupted.

10. In a control system for electric motors, an electric motor, amagnetic brake having a coil in circuit with said motor, and means forsupplying current to said brake coil independently of said motorcircuit.

11. In a control system for electric motors, an electric motor, amagnetic brake having a. coil in circuit with said motor, and anadditional circuit for supplying current to said brake coil.

12. In a control'circuit for electric motors, an electric motor, amagnetic brake having a releasing coil in circuit with said motor, and acircuit including a resistor for supplying current to said coilindependently of said motor circuit.

13. In a control system for electric motors,

an electric motor having an armature and a field winding, a magneticbrake having a releasing coil in circuit with said motor, and acontroller so arranged, when in one position, as to connect said fieldwinding in series with said armature and, when in a second position, toconnect said field winding in shunt to said armature nect an additionalcircuit to said coil.

14. In a control system for electric motors, an electric motor having anarmature and a .a magnetic brake comprising ing in a dynamic brakingcircuit for said motor, and means for supplying current to said coilindependently of said braking circuit.

15. In a. control system, the combination with an electric motor havingan armature and a field winding, anda magnetic brake having a releasingcoil, of a controller comprising variable resistors and so arranged andto con}.

netic'brake having a. coil of a controller so arranged, when in oneposition, as to connest said field winding 'and said armature in serieswith sand c011 and, when in a second position, to connect said fieldWinding in .5

parallel with said armature and to connect an additional circuit betweensaid coil and said Winding. In testimony-whereof, I have hereuntosubscribed my name this 1st day of July 1912. 20

RICHARD J. DEARBORN.

Witnesses:

B. B. HINEs, M. C. MERE.

